Can lessons learned from the Twin Towers' collapse make new buildings safer?

Astronomers are closing in on the proof they've sought for years that one of the most destructive objects in the universe—a supermassive black hole—lurks at the center of our own galaxy. Could it flare up and consume our entire galactic neighborhood? Join NOVA on a mind-bending investigation into one of the most bizarre corners of cosmological science: black hole research. From event horizon to singularity, the elusive secrets of supermassive black holes are revealed through stunning computer-generated imagery, including an extraordinary simulation of what it might look like to fall into the belly of such an all-devouring beast.

In the remote mountains of China, scientist come closer to understanding the origins of flowers.

Can anyone run a marathon? How do you run 26.2 miles if you have trouble making it around the block? With good coaching, discipline, and lots of group support, as NOVA shows when it follows 13 generally sedentary people through a training regimen designed to prepare them for an ultimate test of stamina and endurance. Produced in cooperation with the Boston Athletic Association®, which granted NOVA unprecedented access to the 111th Boston Marathon®, and Tufts University, "Marathon Challenge" takes viewers on a unique adventure inside the human body, tracking the physiological changes that exercise can bring about.